For word of faith critics, tithing is not biblically required, particularly when tithes are used to subsidize private jets, pricey real estate, and other luxurious perks for the pastor. What's more, even though tithing is a common practice in mainline churches also, it would be frowned upon, to say the least, to require a congregant to tithe before paying her own rent.

Prosperity gospel proponents complain that Iowa Republican Sen. Charles Grassley's one-man investigation of six other prosperity ministries (including of Huckabee pal Kenneth Copeland) is an illegal government intrusion into doctrinal disputes. Grassley insists he is not criticizing the doctrine, but only possible abuse of tax-exempt status. But there's no question that the doctrine produces vast amounts of money that are shielded from taxation as well as from disclosure, since churches are not legally required to reveal their finances. If they were, we would all find out exactly how lucrative preaching the prosperity gospel is.

(You won't have to wait much longer to go inside the world of the prosperity gospel. In God's Profits, which is hitting the bookshelves in just a few weeks, I will take you inside the churches, the television studios, and the White House to show how the prosperity gospel has become an integral part of religion, culture, and politics, and you'll read first-hand accounts from believers and former believers. I'll be discussing it on Firedoglake's Book Salon on January 27, at 5:00 p.m. EST.)

This post is excerpted from The FundamentaList, Sarah Posner's weekly countdown of the top news from the religious right at The American Prospect Online.